Some environmentalists warn that a recent federal report on greenhouse gases doesn’t tell the full story. The Environmental Protection Agency says natural gas producers have significantly reduced emissions of methane, a potent heat-trapping gas that could decide whether the fossil fuel is a viable short-term option for fighting climate change.

Chicago's electricity deal booted coal, a big deal to be sure, but it isn't bullish on wind and solar. Some analysts think the deal could do more to promote renewable energy and provide economic benefits in the process.